1. Field of the Invention
The present invention relates to a portable device. More specifically, for example, to a portable device used as a remote control device in a remote keyless entry system for automotive vehicles or the like.
2. Description of Related Art
A remote keyless entry system is a convenient system which allows users to lock and unlock doors only by operating a push button of a small portable device without using a mechanical key. As an advanced type, there is a system which does not require the push button operation with the portable device. With the advanced type system, the user is able to lock and unlock the door by pushing an entry button on the vehicle door or to start engine by pushing a starter button on a dash board in a state of carrying the portable device with him/her, and it is not necessary to take the portable device out from the pocket every time.
The buttery of the portable device of this type may be run out after long time of use, and hence a mechanical key (also referred to as an emergency key) is integrated in the portable device to be used in case of emergency (see JP-A-2004-225350 (Patent Document 1), for example).
<First Related Art>
FIGS. 13A to 13C are drawings illustrating a mechanical-key-integrated portable device. FIG. 13A illustrates a portable device 1 in a state in which a main body 2 and a mechanical key 3 are integrated. Hereinafter, the portable device 1 is referred to as “integrated”. The integrated portable device 1 has an advantage that the mechanical key 3 is user-friendly because it is operated by holding the main body 2 with the hand. However, since the mechanical key 3, which is not normally used, is sticking out from the main body 2, it is a hindrance and the size (specially, the entire length) of the portable device 1 is disadvantageously increased.
<Second Related Art>
As an improved type, for example, as shown in FIG. 13B, a type in which a mechanical key 6 is stored in the interior of a main body 5 of a portable device 4 is conceivable. This is referred to as “stored-type”. A structure in which a head portion Ca of the mechanical key 6 pulled out from the main body 5 of the portable device 4 is preferably attachable to the main body 5. In this configuration, the mechanical key 6 is also user-friendly because it is operated by holding the main body 5 with the hand as in the case of the integrated portable device 1 described above and, in addition, when the mechanical key 6 is not necessary, the mechanical key 6 may be stored in the main body 5, so that the size of the portable device 4 is not increased.
The main body 5 of the portable device 4 has a two-piece structure including an upper case 5a and a lower case 5b as shown in FIG. 13C. In addition, it has a structure in which the upper case 5a and the lower case 5b are separable (for example, a fitting type) considering battery replacement.
Formed between the upper case Ma and the lower case 5b is a storage section 5c for storing the mechanical key 6. For example, when the mechanical key 6 is used to start an engine, the user follows a procedure including steps of:
(1) pulling out the mechanical key 6 from the storage section 5c of the main body 5
(2) attaching the head portion 6a of the mechanical key 6 to the storage section 5c, 
(3) holding the body 5 with the hand,
(4) inserting the mechanical key 6 into a keyhole for starting the engine, and
(5) turning the main body 5 with a required force.
<Third Related Art>
FIG. 14 is a drawing illustrating another example of the stored type. In this drawing, a portable device 7 is the same as the portable device 4 described above (second related art) in that a main body 8 includes an upper case 8a and a lower case 8b of a two-piece type and is different in that a storage section 10 for storing a mechanical key 9 is formed only on one of the cases (the upper case 8a in the drawing), and in that a holding portion 11 is integrally formed at a head portion of the mechanical key 9.
A measure for preventing the mechanical key 9 attached to the storage section 10 of the main body 8 from coming off is achieved by forming a wide portion 9a at part of the mechanical key 9 and using friction between the wide portion 9a and the inner wall of the storage section 10.
However, in the second related art, when an excessive force is applied to the portion of the main body 5 where the mechanical key 6 is mounted (the entry portion of the storage section 5c) in the procedure (5), the upper case 5a and the lower case 5b may disadvantageously come apart (disassembled) unintentionally.
In the third related art, since the storage section 10 for storing the mechanical key 9 is formed only in one of the cases (the upper case 8a in the drawing), the problem in the portable device 4 in the second related art (unintentional disassembly of the case 8) does not occur. However, when the mechanical key 9 is removed from the main body 8, the main body 8 is separated from the mechanical key 9, and hence there arises a problem that the main body 8 or the mechanical key 9 may be lost.
In addition, in the third related art, the measure for preventing the mechanical key 9 from coming off is achieved by friction between the wide portion 9a of the mechanical key 9 and the inner wall of the storage section 10, the friction is gradually reduced with repeated operation of insertion and pulling off of the mechanical key 9, so that the mechanical key 9 may disadvantageously come off easily.